Hydraulic piston pump having distribution through a bi-directional port plate

ABSTRACT

A hydraulic pump having a plurality of pistons sliding in bores formed in a barrel mounted in rotation in a casing of the pump, the barrel bearing against a distribution port plate borne by a cylinder head. Two drainage channels place an inner space of the casing in respective communication with two suction/delivery orifices of the cylinder head. Each drainage channel is provided with a valve able to close the drainage channel in response to an overpressure in the suction/delivery orifice such that, according to the direction of rotation of the pump, the inner space of the casing is in communication through one of the drainage channels with the suction line; whereas the communication through the other drainage channel between the delivery side and the inner space of the casing is closed.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY

This application claims priority to Patent Application No. 1360278 filedOct. 22, 2013 in France, the disclosure of which is incorporated hereinby reference and to which priority is claimed.

FIELD OF THE INVENTION

The present invention relates to a hydraulic piston pump and moreparticularly a hydraulic piston pump in which distribution takes placeby means of a port plate.

BACKGROUND OF THE INVENTION

To allow a piston pump having distribution through a port plate to beable to rotate either to the right or to the left, it is necessary toconstruct this pump, on the one hand, by designing a symmetricaldistribution port plate such that the delivery zone of the pump canbecome a suction zone and vice versa and, on the other hand, byincorporating orifices in the pump which can receive either a suctionconnection or a delivery connection.

According to the direction of rotation of the pump, each of the twoorifices of the pump will become either a suction orifice or a deliveryorifice.

In such an arrangement, the leaks of the distribution port plate on thedelivery side of the pump, which is the pressure side, will be collectedby the casing of the pump.

To evacuate these leaks, it is necessary to provide a connection of thecasing of the pump toward the supply reservoir of the pump by installinga drainage circuit.

This need to have a drainage circuit is a disadvantage.

FR-A-2988143 describes a hydraulic motor with internal drainage. Thehydraulic motor has a drainage orifice communicating with an inner spaceof the casing of the motor, an intermediate pipe into which the drainageorifice of the casing opens, a first nonreturn valve arranged betweenthe intermediate pipe and a first bi-directional hydraulic port and ableto open under the effect of a positive pressure differential between theintermediate pipe and the first bi-directional hydraulic port, and asecond nonreturn valve arranged between the intermediate pipe and asecond bi-directional hydraulic port and able to open under the effectof a positive pressure differential between the intermediate pipe andthe second bi-directional hydraulic port. Such an arrangement makes itpossible for the liquid arising from the internal leaks of the motor tobe evacuated from the casing through the one of the two nonreturn valveswhich is connected to the return port of the motor. In this device, thevalves are closed by default.

SUMMARY OF THE INVENTION

The object of the present invention is to produce a piston pump whichcan rotate either to the right or to the left without having to put inplace a specific pump drainage circuit.

To achieve this aim, the pump according to the present invention has aplurality of pistons sliding in bores formed in a barrel mounted inrotation in a casing of the pump, said barrel bearing against adistribution port plate borne by a cylinder head, said distribution portplate being provided with two symmetrical crescents serving alternatelyas a suction crescent and a delivery crescent according to the directionof rotation of the pump, and is characterized in that the cylinder headis provided with two drainage channels placing an inner space of thecasing in respective communication with two suction/delivery orifices ofsaid cylinder head; each drainage channel being provided with a valveable to close the drainage channel in response to an overpressure in thesuction/delivery orifice such that, according to the direction ofrotation of the pump, the inner space of the casing is in communicationthrough one of the drainage channels with the suction line; whereas thecommunication through the other drainage channel between the deliveryside and the inner space of the casing is closed.

According to one embodiment, the valve has in each case a compressionspring housed in the drainage channel so as to maintain the valve in anopen position by default.

The invention will be better understood, and other aims, details,features and advantages thereof will become more clearly apparent duringthe following description of a number of particular embodiments of theinvention given purely by way of nonlimiting illustrative example withreference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In these drawings:

FIG. 1 is a view in longitudinal section of a known type of hydraulicpiston pump.

FIG. 2 is a view in section on line D-D of FIG. 1.

FIG. 3 is a perspective view of the pump of FIG. 1 rotating to theright.

FIG. 4 is a perspective view of the pump of FIG. 1 rotating to the left.

FIG. 5 is a partial view, in longitudinal section, illustrating theoperation of the suction zone of the pump according to the invention.

FIG. 6 is a partial view, in longitudinal section, illustrating theoperation of the delivery zone of the pump according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1 shows a hydraulic piston pump having a drive shaft 1 providedwith a plate 2 against which there bear a plurality of pistons 3 whichslide in bores 4 formed in a barrel 5 housed in a casing 6 provided witha drainage orifice 8 closed by a cap. The barrel 5 bears against adistribution port plate 7 borne by a cylinder head 9.

In FIG. 2, which is a view in section on D-D of FIG. 1, it can be seenthat, in a known way, the distribution port plate 7 has two crescents 10and 11 which are bean-shaped openings and which are symmetrical.According to the direction of rotation of the shaft 1, these crescentswill serve alternately for suction or for delivery.

FIG. 3 shows the position of the suction pipe A when the drive shaft 1is rotating to the right (or clockwise direction).

FIG. 4 shows the position of this suction pipe A when the drive shaft isrotating to the left (or counter clockwise direction).

A delivery line B, not shown in FIGS. 3 and 4, is connected to the otherorifice of the cylinder head 9.

During the operation of the pump, hydraulic liquid leaks occur on thedelivery side of the pump. These leaks are collected in the casing 6 andwill be evacuated through the drainage orifice 8, which can be connectedto a drainage circuit to return the liquid arising from the leaks to thereservoir.

One aim of the present invention is to dispense with this drainagecircuit.

To achieve this aim, the cylinder head 9 is provided with two nonreturnvalves 12 communicating with the suction/delivery orifices 20.

The effect of these two valves 12 is:

-   -   on the one hand, to allow the inner space 17 of the casing 6 to        communicate freely through one of the valves 12 with the suction        orifice 20 and the suction line A, as is illustrated in FIG. 5,        thereby placing the inner space 17 of the casing 6 in connection        with the suction side of the pump and implementing the drainage        of the pump;    -   on the other hand, closing, through the other valve 12, the        communication of the delivery orifice 20 with the inner space 17        of the casing 6, as is illustrated in FIG. 6.

More precisely, the nonreturn valve has a helical spring 13, a ball 12serving as a valve, and a channel 14 formed in the cylinder head 9 so asto connect in each case the suction/delivery orifice 20 to the innerspace 17 of the casing 6 of the pump. The channel 14 opens into thecasing 6 in line with a peripheral portion of the distribution portplate 7 which has a fluid passage toward the inner space 17 of thecasing 6.

The spring 13 is housed in a wide section of the channel 14, bearingbetween a shoulder of the channel 14 on the casing side and the ball 12on the cylinder head side. By default, the spring 13 maintains the ball12 at a distance from a valve seat 18 surrounding the inlet of thechannel 14. Thus, the channel 14 is open unless there is an overpressurein the suction/delivery orifice 20 with respect to the inner space 17,which is normally at atmospheric pressure. The valve 12 is therefore avalve which is open by default and which closes the channel 14 inresponse to an overpressure in the suction/delivery orifice 20 of thecylinder head.

Although the invention has been described in conjunction with a numberof particular embodiments, it is clearly obvious that it is in no waylimited thereto and that it encompasses all the technical equivalents ofthe means described and combinations thereof where these fall within thescope of the invention.

The use of the verb “have”, “comprise” or “include” and its conjugatedforms does not exclude the presence of elements or steps other thanthose stated in a claim. Unless stated otherwise, the use of theindefinite article “a” for an element does not exclude the presence of aplurality of such elements.

In the claims, any reference sign between parentheses should not beinterpreted as a limitation of the claim.

1. A hydraulic piston pump of the type having a plurality of pistonssliding in bores formed in a barrel mounted in rotation in a casing ofthe pump, said barrel bearing against a distribution port plate borne bya cylinder head, said distribution port plate being provided with twosymmetrical crescents serving alternately as a suction crescent and adelivery crescent according to the direction of rotation of the pump, inwhich the cylinder head is provided with two drainage channels placingan inner space of the casing in respective communication with twosuction/delivery orifices of said cylinder head; each drainage channelbeing provided with a valve, wherein the valve has in each case acompression spring housed in the drainage channel so as to maintain thevalve in an open position by default, the valve being able to close thedrainage channel in response to an overpressure in the suction/deliveryorifice such that, according to the direction of rotation of the pump,the inner space of the casing is in communication through one of thedrainage channels with the suction line; whereas the communicationthrough the other drainage channel between the delivery side and theinner space of the casing is closed.